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Loess
A loess (, ; from ) is a clastic rock, clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loesses or similar deposition (geology), deposits. A loess is a periglacial or aeolian processes, aeolian (windborne) sediment, defined as an accumulation of 20% or less of clay with a balance of roughly equal parts sand and silt (with a typical grain size from 20 to 50 micrometers), often loosely cemented by calcium carbonate. Usually, they are homogeneity and heterogeneity, homogeneous and highly Porosity#Porosity in earth sciences and construction, porous and have vertical capillaries that permit the sediment to fracture and form vertical cliff, bluffs. Properties Loesses are wikt:homogeneous, homogeneous, Porosity#Porosity in earth sciences and construction, porous, friable, pale yellow or buff (color), buff, slightly wikt:coherent, coherent, typically non-stratum, stratified, and often calc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loess Landscape China
A loess (, ; from ) is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loesses or similar deposits. A loess is a periglacial or aeolian (windborne) sediment, defined as an accumulation of 20% or less of clay with a balance of roughly equal parts sand and silt (with a typical grain size from 20 to 50 micrometers), often loosely cemented by calcium carbonate. Usually, they are homogeneous and highly porous and have vertical capillaries that permit the sediment to fracture and form vertical bluffs. Properties Loesses are homogeneous, porous, friable, pale yellow or buff, slightly coherent, typically non- stratified, and often calcareous. Loess grains are angular, with little polishing or rounding, and composed of quartz, feldspar, mica, or other mineral crystals. Loesses have been described as rich, dust-like soil. Loess deposits may become very thick: at more than a h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aeolian Processes
Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erosion, erode, transport, and deposit materials. They are effective agents in regions with sparse vegetation, a lack of soil moisture and a large supply of unconsolidated sediments. Although water is a much more powerful eroding force than wind, aeolian processes are important in arid environments such as deserts. The term is derived from the name of the Greek god Aeolus#Aeolus (son of Hippotes), Aeolus, the keeper of the winds. Definition and setting ''Aeolian processes'' are those processes of erosion, Sediment transport, transport, and Deposition (geology), deposition of sediments that are caused by wind at or near the surface of the earth. Sediment deposits produced by the action of wind and the sedimentary structures characteristic of these deposits are also described as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silt
Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually has a floury feel when dry, and lacks Plasticity (physics), plasticity when wet. Silt can also be felt by the tongue as granular when placed on the front teeth (even when mixed with clay particles). Silt is a common material, making up 45% of average modern mud. It is found in many river deltas and as wind-deposited accumulations, particularly in central Asia, north China, and North America. It is produced in both very hot climates (through such processes as collisions of quartz grains in dust storms) and very cold climates (through such processes as glacial grinding of quartz grains.) Loess is soil rich in silt which makes up some of the most fertile agricultural land on Earth. However, silt is very vulnerable to erosion, and it has poo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Buff (color)
Buff () is a light brownish yellow, ochreous colour, typical of buff leather. Buff is a mixture of yellow ochre and white: two parts of white lead and one part of yellow ochre produces a good buff, or white lead may be tinted with French ochre alone. As an RYB quaternary colour, it is the colour produced by an equal mix of the tertiary colours citron and russet. Etymology The first recorded use of the word ''buff'' to describe a colour was in '' The London Gazette'' of 1686, describing a uniform to be "...a Red Coat with a Buff-colour'd lining". It referred to the colour of undyed buffalo leather, such as soldiers wore as some protection: an eyewitness to the death in the Battle of Edgehill (1642) of Sir Edmund Verney noted "he would neither put on arms rmouror buff coat the day of the battle". Such buff leather was suitable for '' buffing'' or serving as a '' buffer'' between polished objects. It is not clear which bovine "''buffalo''" referred to, but it m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deposition (geology)
Deposition is the geological process in which sediments, soil and rock (geology), rocks are added to a landform or landmass. Wind, ice, water, and gravity Transportation (sediment), transport previously Weathering, weathered surface material, which, at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment. This occurs when the forces responsible for sediment transportation are no longer sufficient to overcome the forces of gravity and friction, creating a resistance to motion; this is known as the null-point hypothesis. Deposition can also refer to the buildup of sediment from Organic matter, organically derived matter or chemical processes. For example, chalk is made up partly of the microscopic calcium carbonate skeletons of marine plankton, the deposition of which induced chemical processes (diagenesis) to deposit further calcium carbonate. Similarly, the formation of coal begins with the deposition of organic material, mainly from plants ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rounding (sediment)
Roundness is the degree of smoothing due to Abrasion (geology), abrasion of sedimentary particles. It is expressed as the ratio of the average radius of curvature of the edges or corners to the radius of curvature of the maximum inscribed sphere. Measure of roundness Rounding, roundness or angularity are terms used to describe the shape of the corners on a particle (or clast) of sediment. Such a particle may be a grain of sand, a pebble, Cobble (geology), cobble or boulder. Although roundness can be numerically quantified, for practical reasons geologists typically use a simple visual chart with up to six categories of roundness: *Very angular: corners sharp and jagged *Angular *Sub-angular *Sub-rounded *Rounded *Well-rounded: corners completely rounded This six-fold category characterisation is used in the Shepard and Young comparison chart and the Powers chart but the Krumbein chart has nine categories. Rounding of sediment particles can indicate the distance and time invol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherent
Coherence is, in general, a state or situation in which all the parts or ideas fit together well so that they form a united whole. More specifically, coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics), an ideal property of waves that enables stationary (i.e. temporally and spatially constant) interference * Coherence (units of measurement), a derived unit that, for a given system of quantities and for a chosen set of base units, is a product of powers of base units with no other proportionality factor than one * Coherence time, the time over which a propagating wave (especially a laser or maser beam) may be considered coherent; the time interval within which its phase is, on average, predictable Mathematics * Coherence (philosophical gambling strategy), a concept in Bayesian statistics * Coherence (signal processing), a statistic that can be used to examine the relation between two signals or data sets * Coherence (statistics), a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratum
In geology and related fields, a stratum (: strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as either '' bedding surfaces'' or ''bedding planes''.Salvador, A. ed., 1994. ''International stratigraphic guide: a guide to stratigraphic classification, terminology, and procedure. 2nd ed.'' Boulder, Colorado, The Geological Society of America, Inc., 215 pp. . Prior to the publication of the International Stratigraphic Guide, older publications have defined a stratum as being either equivalent to a single bed or composed of a number of beds; as a layer greater than 1 cm in thickness and constituting a part of a bed; or a general term that includes both ''bed'' and '' lamina''.Neuendorf, K.K.E., Mehl, Jr., J.P., and Jackson, J.A. , eds., 2005. ''Glossary of Geology'' 5th ed. Alexandria, Virginia, American Geological Institute. 779 pp. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcareous
Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcareous'' is used as an adjectival term applied to anatomical structures which are made primarily of calcium carbonate, in animals such as gastropods, i.e., snails, specifically in relation to such structures as the operculum (gastropod), operculum, the clausilium, and the love dart. The term also applies to the calcium carbonate Test (biology), tests of, often, more-or-less microscopic Foraminifera. Not all tests are calcareous; diatoms and radiolaria have siliceous tests. The molluscs are calcareous organisms, as are the Calcarea, calcareous sponges (Calcarea), that have spicules which are made of calcium carbonate. Additionally, reef-building corals, or Scleractinia, are calcareous organisms that form their rigid skeletal structure th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into fragile elastic plates. This characteristic is described as ''perfect basal cleavage''. Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in sedimentary rock. It is particularly prominent in many granites, pegmatites, and schists, and "books" (large individual crystals) of mica several feet across have been found in some pegmatites. Micas are used in products such as drywalls, paints, and fillers, especially in parts for automobiles, roofing, and in electronics. The mineral is used in cosmetics and food to add "shimmer" or "frost". Properties and structure The mica group comprises 37 phyllosilicate minerals. All crystallize in the monoclinic system, with a tendency towards pseudohexagonal crystals, and are similar in structure but vary in chemical composition. Micas are translucent to opa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of Silicon dioxide, SiO2. Quartz is, therefore, classified structurally as a Silicate mineral#Tectosilicates, framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at . Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz, several of which are classifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
